It happened inside the LA Fitness on Deer Park Avenue around 7:15 p.m. Tuesday.
Police say Noah Haynes and a 17-year-old male were involved in a verbal altercation when staff members inside the gym asked them to leave.
The two then got into a physical fight in the parking lot. Haynes left the premises in a car, while the 17-year-old returned to the gym.
Haynes returned approximately 30 minutes later, entered the building, and confronted the 17-year-old in the locker room.
Police say Haynes slashed the teen in the neck with a metal object and pointed a handgun at him.
The two left the locker room and began to fight in the gym area.
The victim yelled to other people in the gym that Haynes had a gun.
Three gym members intervened and held Haynes down until police arrived.
Police say Haynes fired one shot during the struggle. No one was struck by the bullet.
Several witnesses called 911 at approximately 7:50 p.m. to report an active shooter.
Police officers placed Haynes in custody at 7:55 p.m. The 17-year-old was transported to a local hospital, treated for minor injuries, and released.
Haynes, of Wyandanch, was charged with second-degree assault, reckless endangerment, menacing, and criminal possession of a weapon.
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